Paxillus involutus is a widely distributed, variable species found under a variety of trees. Its gills are its most distinctive feature: they stain brown when damaged, and they are separable as a layer (push with a fingertip just above the apex of the stem). In northern and montane areas of North America, Paxillus involutus should be compared with Paxillus vernalis, which is nearly identical but features a somewhat wider stem (2-4 cm) and grows under quaking aspen and paper birch.

The Paxillus involutus group has been subjected to both mating studies (Fries, 1985) and DNA analysis (Jarosch & Bresinski, 1999), along with traditional morphological analyses--and results have upheld the idea that Paxillus involutus and Paxillus vernalis are biologically and genetically distinct, though they are difficult to separate on the basis of physical features.

Description:

Ecology: Mycorrhizal with a wide variety of hardwoods and conifers; apparently also capable of existing as a saprobe on wood; found in woods and in urban settings; growing alone, scattered, or gregariously; summer and fall; widely distributed in North America.